30079_38b.pdf

(912 KB) Pobierz
Fig. 38.16 Flow diagram.
These handling methods are implemented individually, or in combination, by commercially available
material-handling equipment types.
38.5 MATERIAL-HANDLING EQUIPMENT CONSIDERATIONS AND EXAMPLES
38.5.1 Developing the Plan
Once the material-handling problem has been identified and the relevant data have been collected
and analyzed, the next step in the design process is to develop a plan for solving the problem. This
usually involves the design and/or selection of appropriate types, sizes, and capacities of material-
handling equipment. In order to properly select material handling equipment, it must be realized that
in most cases, the solution to the problem does not consist merely of selecting a particular piece of
815044735.002.png
Fig. 38.17 "From-to" chart.
hardware, such as a section of conveyor. Rather, handling should be viewed as part of an overall
system, with all activities interrelated and meshing together. Only on this basis can the best overall
type of equipment or system be planned.
This section provides examples of some of the more common types of unit load material handling
and storage equipment used in production facilities.
38.5.2 Conveyors
Conveyors are generally used to transport materials long distances over fixed paths. Their function
may be solely the movement of items from one location in a process or facility to another point, or
they may move items through various stages of receiving, processing, assembly, finishing, inspection,
packaging, sortation, and shipping.
Conveyors used in material handing are of two basic types:
1. Gravity conveyors, including chutes, slides, and gravity wheel or roller conveyors that essen-
tially exploit the use of gravity to move items from a point at a relatively high elevation to
another point at a lower elevation. As listed in Fig. 38.12, MHI Principle 5 indicates that one
should maximize the use of gravity in designing material-handling systems.
2. Powered conveyors, which generally use electric motors to drive belts, chains, or rollers in a
variety of in-floor, floor-mounted, or overhead configurations.
In general, conveyors are employed in unit material handling when
1. Loads are uniform.
2. Materials move continuously.
3. Routes do not vary.
4. Load is constant.
5. Movement rate is relatively fixed.
6. Cross traffic can be bypassed.
815044735.003.png
REASON
Material Flow
Share Equipment
Parts Subassembly
Ease of Supervision
Noise Avoidance
Fig. 38.18 Activity relationship chart.
815044735.004.png
Fig. 38.19 Unit load design.
7. Path is relatively fixed.
8. Movement is point-to-point.
9. Automatic counting, sorting, weighing, or dispatching is needed.
10. In-process storage is required.
11. In-process inspection is required.
12. Production pacing is necessary.
13. Process control is required.
14. Controlled flow is needed.
15. Materials are handled at extreme temperatures, or other adverse conditions.
16. Handling is required in a hazardous area.
17. Hazardous materials are handled.
18. Machines are integrated into a system.
19. Robots are integrated into a system.
20. Materials are moved between workplaces.
21. Manual handling and/or lifting is undesirable.
815044735.005.png
Fig. 38.20 Example pallet-loading patterns.
22. Changes in production volume or pace are needed.
23. Visual surveillance of a production process is required.
24. Floor space can be saved by utilizing overhead space.
25. Flexibility is required to meet changes in production processes.
26. Integration between computer-aided design and computer-aided manufacturing is required.
This section further details essential information on four main classes of conveyors used in unit
material handling:
1. Gravity conveyors
2. Powered conveyors
3. Chain-driven conveyors
4. Power-and-free conveyors
Gravity Conveyors
Gravity conveyors exploit gravity to move material without the use of other forms of energy. Chutes,
skate wheel conveyors, and roller conveyors are the most common forms of gravity conveyors. Figure
38.23 illustrates wheel and roller conveyors. Advantages of gravity conveyors are low cost, relatively
low maintenance, and negligible breakdown rate. The main requirement for using gravity conveyors
is the ability to provide the necessary gradient in the system configuration at the point at which
gravity units are placed.
815044735.001.png

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika:

Zgłoś jeśli naruszono regulamin